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Millan R, Jager E, Mouginot J, Wood MH, Larsen SH, Mathiot P, Jourdain NC, Bjørk A. Rapid disintegration and weakening of ice shelves in North Greenland. Nat Commun 2023; 14:6914. [PMID: 37935697 PMCID: PMC10630314 DOI: 10.1038/s41467-023-42198-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2023] [Accepted: 10/03/2023] [Indexed: 11/09/2023] Open
Abstract
The glaciers of North Greenland are hosting enough ice to raise sea level by 2.1 m, and have long considered to be stable. This part of Greenland is buttressed by the last remaining ice shelves of the ice sheet. Here, we show that since 1978, ice shelves in North Greenland have lost more than 35% of their total volume, three of them collapsing completely. For the floating ice shelves that remain we observe a widespread increase in ice shelf mass losses, that are dominated by enhanced basal melting rates. Between 2000 and 2020, there was a widespread increase in basal melt rates that closely follows a rise in the ocean temperature. These glaciers are showing a direct dynamical response to ice shelf changes with retreating grounding lines and increased ice discharge. These results suggest that, under future projections of ocean thermal forcing, basal melting rates will continue to rise or remain at high level, which may have dramatic consequences for the stability of Greenlandic glaciers.
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Affiliation(s)
- R Millan
- Université Grenoble Alpes, CNRS, IRD, INP, 38400, Grenoble, Isère, France.
| | - E Jager
- Université Grenoble Alpes, CNRS, IRD, INP, 38400, Grenoble, Isère, France
| | - J Mouginot
- Université Grenoble Alpes, CNRS, IRD, INP, 38400, Grenoble, Isère, France
| | - M H Wood
- Moss Landing Marine Laboratories, San José State University, San Jose, CA, 95192, USA
| | - S H Larsen
- Department of Glaciology and Climate, Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark
| | - P Mathiot
- Université Grenoble Alpes, CNRS, IRD, INP, 38400, Grenoble, Isère, France
| | - N C Jourdain
- Université Grenoble Alpes, CNRS, IRD, INP, 38400, Grenoble, Isère, France
| | - A Bjørk
- Department of Geosciences and Natural Resources Management, University of Copenhagen, 1350, Copenhagen, Denmark
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2
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Chudley TR, Howat IM, King MD, Negrete A. Atlantic water intrusion triggers rapid retreat and regime change at previously stable Greenland glacier. Nat Commun 2023; 14:2151. [PMID: 37076489 PMCID: PMC10115864 DOI: 10.1038/s41467-023-37764-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 03/30/2023] [Indexed: 04/21/2023] Open
Abstract
Ice discharge from Greenland's marine-terminating glaciers contributes to half of all mass loss from the ice sheet, with numerous mechanisms proposed to explain their retreat. Here, we examine K.I.V Steenstrups Nordre Bræ ('Steenstrup') in Southeast Greenland, which, between 2018 and 2021, retreated ~7 km, thinned ~20%, doubled in discharge, and accelerated ~300%. This rate of change is unprecedented amongst Greenland's glaciers and now places Steenstrup in the top 10% of glaciers by contribution to ice-sheet-wide discharge. In contrast to expected behaviour from a shallow, grounded tidewater glacier, Steenstrup was insensitive to high surface temperatures that destabilised many regional glaciers in 2016, appearing instead to respond to a >2 °C anomaly in deeper Atlantic water (AW) in 2018. By 2021, a rigid proglacial mélange had developed alongside notable seasonal variability. Steenstrup's behaviour highlights that even long-term stable glaciers with high sills are vulnerable to sudden and rapid retreat from warm AW intrusion.
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Affiliation(s)
- T R Chudley
- Byrd Polar and Climate Research Center, Ohio State University, Columbus, OH, USA.
- Department of Geography, Durham University, Durham, UK.
| | - I M Howat
- Byrd Polar and Climate Research Center, Ohio State University, Columbus, OH, USA
- School of Earth Sciences, Ohio State University, Columbus, OH, USA
| | - M D King
- Polar Science Center, University of Washington, Seattle, WA, USA
| | - A Negrete
- Byrd Polar and Climate Research Center, Ohio State University, Columbus, OH, USA
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3
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Modern temperatures in central-north Greenland warmest in past millennium. Nature 2023; 613:503-507. [PMID: 36653569 PMCID: PMC9849122 DOI: 10.1038/s41586-022-05517-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Accepted: 11/01/2022] [Indexed: 01/20/2023]
Abstract
The Greenland Ice Sheet has a central role in the global climate system owing to its size, radiative effects and freshwater storage, and as a potential tipping point1. Weather stations show that the coastal regions are warming2, but the imprint of global warming in the central part of the ice sheet is unclear, owing to missing long-term observations. Current ice-core-based temperature reconstructions3-5 are ambiguous with respect to isolating global warming signatures from natural variability, because they are too noisy and do not include the most recent decades. By systematically redrilling ice cores, we created a high-quality reconstruction of central and north Greenland temperatures from AD 1000 until 2011. Here we show that the warming in the recent reconstructed decade exceeds the range of the pre-industrial temperature variability in the past millennium with virtual certainty (P < 0.001) and is on average 1.5 ± 0.4 degrees Celsius (1 standard error) warmer than the twentieth century. Our findings suggest that these exceptional temperatures arise from the superposition of natural variability with a long-term warming trend, apparent since AD 1800. The disproportionate warming is accompanied by enhanced Greenland meltwater run-off, implying that anthropogenic influence has also arrived in central and north Greenland, which might further accelerate the overall Greenland mass loss.
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4
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Adams JK, Dean BY, Athey SN, Jantunen LM, Bernstein S, Stern G, Diamond ML, Finkelstein SA. Anthropogenic particles (including microfibers and microplastics) in marine sediments of the Canadian Arctic. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 784:147155. [PMID: 34088044 DOI: 10.1016/j.scitotenv.2021.147155] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 04/09/2021] [Accepted: 04/11/2021] [Indexed: 05/06/2023]
Abstract
We report the first Canadian Arctic-wide study of anthropogenic particles (APs, >125 μm), including microfibers (synthetic, semi-synthetic and anthropogenically modified cellulose) and microplastics, in marine sediments from 14 sites. Samples from across the Canadian Arctic were collected between 2014 and 2017 from onboard the CCGS Amundsen. Samples were processed using density separation with calcium chloride (CaCl2). APs >125 μm were identified and a subset (22%) were characterized using Raman spectroscopy. Following blank-correction, microfiber numbers were corrected using Raman data in a novel approach to subtract possible "natural" cellulose microfibers with no anthropogenic signal via Raman spectroscopy, to estimate the proportion of cellulose microfibers that are of confirmed anthropogenic origin. Of all microfibers examined by Raman spectroscopy, 51% were anthropogenic cellulose, 11% were synthetic polymers, and 7% were extruded fibers emitting a dye signal. The remaining 31% of microfibers were identified as cellulosic but could not be confirmed as anthropogenic and thus were excluded from the final concentrations. Concentrations of confirmed APs in sediments ranged from 0.6 to 4.7 particles g-1 dry weight (dw). Microfibers comprised 82% of all APs, followed by fragments at 15%. Total microfiber concentrations ranged from 0.4 to 3.2 microfibers g-1 dw, while microplastic (fragments, foams, films and spheres) concentrations ranged from 0 to 1.6 microplastics g-1 dw. These concentrations may exceed those recorded in urban areas near point sources of plastic pollution, and indicate that the Canadian Arctic is a sink for APs, including anthropogenic cellulose fibers. Overall, we provide an important benchmark of AP contamination in Canadian Arctic marine sediments against which to measure temporal trends, including the effects of source reduction strategies and climate change, both of which will likely alter patterns of accumulation of anthropogenic particles.
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Affiliation(s)
- Jennifer K Adams
- Department of Earth Sciences, University of Toronto, 22 Ursula Franklin Street, Toronto, Ontario M5S 3B1, Canada
| | - Bethany Y Dean
- Air Quality Processes Research Section, Environment and Climate Change Canada, 6248 Eighth Line, Egbert, ON L0L1N0, Canada
| | - Samantha N Athey
- Department of Earth Sciences, University of Toronto, 22 Ursula Franklin Street, Toronto, Ontario M5S 3B1, Canada
| | - Liisa M Jantunen
- Department of Earth Sciences, University of Toronto, 22 Ursula Franklin Street, Toronto, Ontario M5S 3B1, Canada; Air Quality Processes Research Section, Environment and Climate Change Canada, 6248 Eighth Line, Egbert, ON L0L1N0, Canada
| | - Sarah Bernstein
- Air Quality Processes Research Section, Environment and Climate Change Canada, 6248 Eighth Line, Egbert, ON L0L1N0, Canada
| | - Gary Stern
- University of Manitoba, 586 Wallace Bld, 125 Dysart Rd. Winnipeg, Manitoba R3T 2N2, Canada
| | - Miriam L Diamond
- Department of Earth Sciences, University of Toronto, 22 Ursula Franklin Street, Toronto, Ontario M5S 3B1, Canada; School of the Environment, University of Toronto, 33 Willcocks St., Toronto, Ontario M5S 3E8, Canada
| | - Sarah A Finkelstein
- Department of Earth Sciences, University of Toronto, 22 Ursula Franklin Street, Toronto, Ontario M5S 3B1, Canada.
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5
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Sellevold R, Vizcaíno M. Global Warming Threshold and Mechanisms for Accelerated Greenland Ice Sheet Surface Mass Loss. JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS 2020; 12:e2019MS002029. [PMID: 33042389 PMCID: PMC7540049 DOI: 10.1029/2019ms002029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 06/14/2020] [Accepted: 06/28/2020] [Indexed: 06/11/2023]
Abstract
The Community Earth System Model version 2.1 (CESM2.1) is used to investigate the evolution of the Greenland ice sheet (GrIS) surface mass balance (SMB) under an idealized CO2 forcing scenario of 1% increase until stabilization at 4× pre-industrial at model year 140. In this simulation, the SMB calculation is coupled with the atmospheric model, using a physically based surface energy balance scheme for melt, explicit calculation of snow albedo, and a realistic treatment of polar snow and firn compaction. By the end of the simulation (years 131-150), the SMB decreases with 994 Gt yr-1 with respect to the pre-industrial SMB, which represents a sea-level rise contribution of 2.8 mm yr-1. For a threshold of 2.7-K global temperature increase with respect to pre-industrial, the rate of expansion of the ablation area increases, the mass loss accelerates due to loss of refreezing capacity and accelerated melt, and the SMB becomes negative 6 years later. Before acceleration, longwave radiation is the most important contributor to increasing energy for melt. After acceleration, the large expansion of the ablation area strongly reduces surface albedo. This and much increased turbulent heat fluxes as the GrIS-integrated summer surface temperature approaches melt point become the major sources of energy for melt.
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Affiliation(s)
- Raymond Sellevold
- Geoscience and Remote SensingDelft University of TechnologyDelftthe Netherlands
| | - Miren Vizcaíno
- Geoscience and Remote SensingDelft University of TechnologyDelftthe Netherlands
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6
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Smith B, Fricker HA, Gardner AS, Medley B, Nilsson J, Paolo FS, Holschuh N, Adusumilli S, Brunt K, Csatho B, Harbeck K, Markus T, Neumann T, Siegfried MR, Zwally HJ. Pervasive ice sheet mass loss reflects competing ocean and atmosphere processes. Science 2020; 368:1239-1242. [PMID: 32354841 DOI: 10.1126/science.aaz5845] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Accepted: 04/13/2020] [Indexed: 01/07/2023]
Abstract
Quantifying changes in Earth's ice sheets and identifying the climate drivers are central to improving sea level projections. We provide unified estimates of grounded and floating ice mass change from 2003 to 2019 using NASA's Ice, Cloud and land Elevation Satellite (ICESat) and ICESat-2 satellite laser altimetry. Our data reveal patterns likely linked to competing climate processes: Ice loss from coastal Greenland (increased surface melt), Antarctic ice shelves (increased ocean melting), and Greenland and Antarctic outlet glaciers (dynamic response to ocean melting) was partially compensated by mass gains over ice sheet interiors (increased snow accumulation). Losses outpaced gains, with grounded-ice loss from Greenland (200 billion tonnes per year) and Antarctica (118 billion tonnes per year) contributing 14 millimeters to sea level. Mass lost from West Antarctica's ice shelves accounted for more than 30% of that region's total.
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Affiliation(s)
- Ben Smith
- Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA, USA.
| | - Helen A Fricker
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Alex S Gardner
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Brooke Medley
- Cryospheric Science Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - Johan Nilsson
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Fernando S Paolo
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Nicholas Holschuh
- Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA.,Department of Geology, Amherst College, Amherst, MA, USA
| | - Susheel Adusumilli
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Kelly Brunt
- Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA
| | - Bea Csatho
- Department of Geological Sciences, University at Buffalo, Buffalo, NY, USA
| | | | - Thorsten Markus
- Cryospheric Science Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - Thomas Neumann
- Cryospheric Science Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | | | - H Jay Zwally
- Cryospheric Science Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA.,Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA
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7
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Rigét F, Vorkamp K, Eulaers I, Dietz R. Influence of climate and biological variables on temporal trends of persistent organic pollutants in Arctic char and ringed seals from Greenland. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2020; 22:993-1005. [PMID: 32083628 DOI: 10.1039/c9em00561g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Climate change may affect temporal trends of persistent organic pollutants (POPs) in Arctic wildlife. We studied how biological and climate variables influence temporal trends of selected POP groups in landlocked Arctic char muscle and in ringed seal blubber from West and East Greenland. The variables included fish length or animal age, sex, a stable nitrogen isotope, sea ice extent, air or seawater temperature, salinity and the Arctic Oscillation Index (AOI). Model selection for multiple regression showed that the most important predictors varied among POP groups, species and region. Decreasing time trends were found for all POP groups with the exception of hexachlorobenzene (HCB) concentration which remained stable in Arctic char and ringed seals from West Greenland. When retained in the most parsimonious model, the AOI was positively associated with POP concentrations for East Greenland seals, but negatively for West Greenland seals. Seawater temperature and sea ice extent were positively associated with POP concentrations. The effects of explanatory variables on the annual rates of change in POP concentrations were relatively minor relative to the decline caused by reduction in POP emissions following national and international regulations introduced since the 1970s.
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Affiliation(s)
- Frank Rigét
- Aarhus University, Department of Bioscience, Roskilde, Denmark.
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8
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Mass balance of the Greenland Ice Sheet from 1992 to 2018. Nature 2019; 579:233-239. [DOI: 10.1038/s41586-019-1855-2] [Citation(s) in RCA: 257] [Impact Index Per Article: 51.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Accepted: 11/25/2019] [Indexed: 01/13/2023]
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9
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Rohling EJ, Hibbert FD, Grant KM, Galaasen EV, Irvalı N, Kleiven HF, Marino G, Ninnemann U, Roberts AP, Rosenthal Y, Schulz H, Williams FH, Yu J. Asynchronous Antarctic and Greenland ice-volume contributions to the last interglacial sea-level highstand. Nat Commun 2019; 10:5040. [PMID: 31695032 PMCID: PMC6834665 DOI: 10.1038/s41467-019-12874-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 10/07/2019] [Indexed: 11/23/2022] Open
Abstract
The last interglacial (LIG; ~130 to ~118 thousand years ago, ka) was the last time global sea level rose well above the present level. Greenland Ice Sheet (GrIS) contributions were insufficient to explain the highstand, so that substantial Antarctic Ice Sheet (AIS) reduction is implied. However, the nature and drivers of GrIS and AIS reductions remain enigmatic, even though they may be critical for understanding future sea-level rise. Here we complement existing records with new data, and reveal that the LIG contained an AIS-derived highstand from ~129.5 to ~125 ka, a lowstand centred on 125–124 ka, and joint AIS + GrIS contributions from ~123.5 to ~118 ka. Moreover, a dual substructure within the first highstand suggests temporal variability in the AIS contributions. Implied rates of sea-level rise are high (up to several meters per century; m c−1), and lend credibility to high rates inferred by ice modelling under certain ice-shelf instability parameterisations. The relative contributions of the Greenland and Antarctic Ice Sheets to Last Interglacial sea level rise remain debated, as do the timing and magnitude. Here, data show that the Antarctic Ice Sheet dominated particularly high levels of sea-level rise during the early Last Interglacial.
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Affiliation(s)
- Eelco J Rohling
- Research School of Earth Sciences, The Australian National University, Canberra, ACT, 2601, Australia. .,Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, SO14 3ZH, UK.
| | - Fiona D Hibbert
- Research School of Earth Sciences, The Australian National University, Canberra, ACT, 2601, Australia.
| | - Katharine M Grant
- Research School of Earth Sciences, The Australian National University, Canberra, ACT, 2601, Australia
| | - Eirik V Galaasen
- Department of Earth Science and Bjerknes Centre for Climate Research, University of Bergen, Allegaten 41, 5007, Bergen, Norway
| | - Nil Irvalı
- Department of Earth Science and Bjerknes Centre for Climate Research, University of Bergen, Allegaten 41, 5007, Bergen, Norway
| | - Helga F Kleiven
- Department of Earth Science and Bjerknes Centre for Climate Research, University of Bergen, Allegaten 41, 5007, Bergen, Norway
| | - Gianluca Marino
- Research School of Earth Sciences, The Australian National University, Canberra, ACT, 2601, Australia.,Department of Marine Geosciences and Territorial Planning, University of Vigo, 36310, Vigo, Spain
| | - Ulysses Ninnemann
- Department of Earth Science and Bjerknes Centre for Climate Research, University of Bergen, Allegaten 41, 5007, Bergen, Norway
| | - Andrew P Roberts
- Research School of Earth Sciences, The Australian National University, Canberra, ACT, 2601, Australia
| | - Yair Rosenthal
- Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ, 08903, USA
| | - Hartmut Schulz
- Department of Geology and Paleontology, University of Tuebingen, Sigwartstrasse 10, D-7400, Tuebingen, Germany
| | - Felicity H Williams
- Research School of Earth Sciences, The Australian National University, Canberra, ACT, 2601, Australia
| | - Jimin Yu
- Research School of Earth Sciences, The Australian National University, Canberra, ACT, 2601, Australia
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10
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Satellite Remote Sensing of the Greenland Ice Sheet Ablation Zone: A Review. REMOTE SENSING 2019. [DOI: 10.3390/rs11202405] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The Greenland Ice Sheet is now the largest land ice contributor to global sea level rise, largely driven by increased surface meltwater runoff from the ablation zone, i.e., areas of the ice sheet where annual mass losses exceed gains. This small but critically important area of the ice sheet has expanded in size by ~50% since the early 1960s, and satellite remote sensing is a powerful tool for monitoring the physical processes that influence its surface mass balance. This review synthesizes key remote sensing methods and scientific findings from satellite remote sensing of the Greenland Ice Sheet ablation zone, covering progress in (1) radar altimetry, (2) laser (lidar) altimetry, (3) gravimetry, (4) multispectral optical imagery, and (5) microwave and thermal imagery. Physical characteristics and quantities examined include surface elevation change, gravimetric mass balance, reflectance, albedo, and mapping of surface melt extent and glaciological facies and zones. The review concludes that future progress will benefit most from methods that combine multi-sensor, multi-wavelength, and cross-platform datasets designed to discriminate the widely varying surface processes in the ablation zone. Specific examples include fusing laser altimetry, radar altimetry, and optical stereophotogrammetry to enhance spatial measurement density, cross-validate surface elevation change, and diagnose radar elevation bias; employing dual-frequency radar, microwave scatterometry, or combining radar and laser altimetry to map seasonal snow depth; fusing optical imagery, radar imagery, and microwave scatterometry to discriminate between snow, liquid water, refrozen meltwater, and bare ice near the equilibrium line altitude; combining optical reflectance with laser altimetry to map supraglacial lake, stream, and crevasse bathymetry; and monitoring the inland migration of snowlines, surface melt extent, and supraglacial hydrologic features.
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11
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Noël B, van de Berg WJ, Lhermitte S, van den Broeke MR. Rapid ablation zone expansion amplifies north Greenland mass loss. SCIENCE ADVANCES 2019; 5:eaaw0123. [PMID: 31517042 PMCID: PMC6726448 DOI: 10.1126/sciadv.aaw0123] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Accepted: 08/06/2019] [Indexed: 05/02/2023]
Abstract
Since the early 1990s, the Greenland ice sheet (GrIS) has been losing mass at an accelerating rate, primarily due to enhanced meltwater runoff following atmospheric warming. Here, we show that a pronounced latitudinal contrast exists in the GrIS response to recent warming. The ablation area in north Greenland expanded by 46%, almost twice as much as in the south (+25%), significantly increasing the relative contribution of the north to total GrIS mass loss. This latitudinal contrast originates from a different response to the recent change in large-scale Arctic summertime atmospheric circulation, promoting southwesterly advection of warm air toward the GrIS. In the southwest, persistent high atmospheric pressure reduced cloudiness, increasing runoff through enhanced absorption of solar radiation; in contrast, increased early-summer cloudiness in north Greenland enhanced atmospheric warming through decreased longwave heat loss. This triggered a rapid snowline retreat, causing early bare ice exposure, amplifying northern runoff.
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Affiliation(s)
- Brice Noël
- Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, Netherlands
| | | | - Stef Lhermitte
- Department of Geoscience and Remote Sensing, Delft University of Technology, Delft, Netherlands
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12
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Aschwanden A, Fahnestock MA, Truffer M, Brinkerhoff DJ, Hock R, Khroulev C, Mottram R, Khan SA. Contribution of the Greenland Ice Sheet to sea level over the next millennium. SCIENCE ADVANCES 2019; 5:eaav9396. [PMID: 31223652 PMCID: PMC6584365 DOI: 10.1126/sciadv.aav9396] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 05/14/2019] [Indexed: 05/22/2023]
Abstract
The Greenland Ice Sheet holds 7.2 m of sea level equivalent and in recent decades, rising temperatures have led to accelerated mass loss. Current ice margin recession is led by the retreat of outlet glaciers, large rivers of ice ending in narrow fjords that drain the interior. We pair an outlet glacier-resolving ice sheet model with a comprehensive uncertainty quantification to estimate Greenland's contribution to sea level over the next millennium. We find that Greenland could contribute 5 to 33 cm to sea level by 2100, with discharge from outlet glaciers contributing 8 to 45% of total mass loss. Our analysis shows that uncertainties in projecting mass loss are dominated by uncertainties in climate scenarios and surface processes, whereas uncertainties in calving and frontal melt play a minor role. We project that Greenland will very likely become ice free within a millennium without substantial reductions in greenhouse gas emissions.
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Affiliation(s)
- Andy Aschwanden
- University of Alaska Fairbanks, 2156 Koyukuk Dr., Fairbanks, AK 99775, USA
| | - Mark A. Fahnestock
- University of Alaska Fairbanks, 2156 Koyukuk Dr., Fairbanks, AK 99775, USA
| | - Martin Truffer
- University of Alaska Fairbanks, 2156 Koyukuk Dr., Fairbanks, AK 99775, USA
| | | | - Regine Hock
- University of Alaska Fairbanks, 2156 Koyukuk Dr., Fairbanks, AK 99775, USA
| | | | - Ruth Mottram
- Danish Meteorological Institute, Copenhagen, Denmark
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13
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Abstract
We reconstruct the mass balance of the Greenland Ice Sheet for the past 46 years by comparing glacier ice discharge into the ocean with interior accumulation of snowfall from regional atmospheric climate models over 260 drainage basins. The mass balance started to deviate from its natural range of variability in the 1980s. The mass loss has increased sixfold since the 1980s. Greenland has raised sea level by 13.7 mm since 1972, half during the last 8 years. We reconstruct the mass balance of the Greenland Ice Sheet using a comprehensive survey of thickness, surface elevation, velocity, and surface mass balance (SMB) of 260 glaciers from 1972 to 2018. We calculate mass discharge, D, into the ocean directly for 107 glaciers (85% of D) and indirectly for 110 glaciers (15%) using velocity-scaled reference fluxes. The decadal mass balance switched from a mass gain of +47 ± 21 Gt/y in 1972–1980 to a loss of 51 ± 17 Gt/y in 1980–1990. The mass loss increased from 41 ± 17 Gt/y in 1990–2000, to 187 ± 17 Gt/y in 2000–2010, to 286 ± 20 Gt/y in 2010–2018, or sixfold since the 1980s, or 80 ± 6 Gt/y per decade, on average. The acceleration in mass loss switched from positive in 2000–2010 to negative in 2010–2018 due to a series of cold summers, which illustrates the difficulty of extrapolating short records into longer-term trends. Cumulated since 1972, the largest contributions to global sea level rise are from northwest (4.4 ± 0.2 mm), southeast (3.0 ± 0.3 mm), and central west (2.0 ± 0.2 mm) Greenland, with a total 13.7 ± 1.1 mm for the ice sheet. The mass loss is controlled at 66 ± 8% by glacier dynamics (9.1 mm) and 34 ± 8% by SMB (4.6 mm). Even in years of high SMB, enhanced glacier discharge has remained sufficiently high above equilibrium to maintain an annual mass loss every year since 1998.
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14
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Accelerating changes in ice mass within Greenland, and the ice sheet's sensitivity to atmospheric forcing. Proc Natl Acad Sci U S A 2019; 116:1934-1939. [PMID: 30670639 PMCID: PMC6369742 DOI: 10.1073/pnas.1806562116] [Citation(s) in RCA: 120] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The recent deglaciation of Greenland is a response to both oceanic and atmospheric forcings. From 2000 to 2010, ice loss was concentrated in the southeast and northwest margins of the ice sheet, in large part due to the increasing discharge of marine-terminating outlet glaciers, emphasizing the importance of oceanic forcing. However, the largest sustained (∼10 years) acceleration detected by Gravity Recovery and Climate Experiment (GRACE) occurred in southwest Greenland, an area largely devoid of such glaciers. The sustained acceleration and the subsequent, abrupt, and even stronger deceleration were mostly driven by changes in air temperature and solar radiation. Continued atmospheric warming will lead to southwest Greenland becoming a major contributor to sea level rise. From early 2003 to mid-2013, the total mass of ice in Greenland declined at a progressively increasing rate. In mid-2013, an abrupt reversal occurred, and very little net ice loss occurred in the next 12–18 months. Gravity Recovery and Climate Experiment (GRACE) and global positioning system (GPS) observations reveal that the spatial patterns of the sustained acceleration and the abrupt deceleration in mass loss are similar. The strongest accelerations tracked the phase of the North Atlantic Oscillation (NAO). The negative phase of the NAO enhances summertime warming and insolation while reducing snowfall, especially in west Greenland, driving surface mass balance (SMB) more negative, as illustrated using the regional climate model MAR. The spatial pattern of accelerating mass changes reflects the geography of NAO-driven shifts in atmospheric forcing and the ice sheet’s sensitivity to that forcing. We infer that southwest Greenland will become a major future contributor to sea level rise.
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